1. Field of the Invention
The present invention relates to a projection display apparatus and an image forming apparatus.
2. Description of the Related Art
A conventional projection display apparatus includes a light source, a light modulating device, and a projection lens. The light source takes the form of, for example, light emitting diodes (LEDs) or a discharge lamp (e.g., halogen lamp). The light modulating device takes the form of a liquid crystal panel or a digital micro mirror device in which light is reflected by individual pixels in specific directions. The liquid crystal panel includes a number of pixels each of which is driven or modulated in accordance with an image signal to transmit or block the light emitted from the light source. The projection lens projects the modulated light signals onto a screen.
A conventional projection display apparatus requires a light source that emits light at all times. Energizing a light source at all times consumes a large amount of electric power and therefore generates a large amount of heat.